1. Field of the Invention
The present invention relates to an ink jet recording apparatus that records by discharging ink from recording means to a recording medium. The invention also relates to a method for discharge recovery thereof.
2. Related Background Art
A recording apparatus provided with the functions of printer, copying machine, facsimile, and the like or a recording apparatus, which is used as an output terminal for a complex type electronic equipment or a work station including a computer, a word processor, or the like, is structured to record images (including characters, symbols, or the like) on a recording medium (recording material), such as a paper sheet, a thin plastic sheet, in accordance with recording information. Then, by the recording methods adopted, such recording apparatuses are classified into those of an ink jet type, a wire-dot type, a thermal type, a laser beam type, among some others, respectively.
For a recording apparatus of a serial type where recording is performed, while the main scan is being made in the direction intersecting the carrying direction (sub-scanning direction) of a recording medium, images are recorded (main scanned) by recording means (a recording head) that travels along the recording medium, and when recording on a one-line portion is completed, the recording medium is conveyed in a given amount (a pitch feeding for the sub-scanning). Then, recording is resumed on the recording medium that has come to a stop again. Thus, the images on the next line portion are recorded (main scanned). These operations are repeated to complete recording on the entire area of the recording medium.
On the other hand, for a recording apparatus of a line type where recording is performed only by the sub-scans in the carrying direction of a recording medium, the recording medium is set at a given recording position, and the sheet conveyance (pitch feeding) is made for a given amount, while recording on the one-line portion is being performed altogether and in continuation, thus recording images on the entire area of the recording medium.
Of the recording apparatuses described above, the ink jet type (an ink jet recording apparatus) is such that recording is made by discharging ink from recording means (recording head) to a recording medium, which facilitates making the recording means compact to record images in high precision at high speed, and that recording is made on an ordinary paper sheet without any particular treatment given to it. As a result, its running costs are made lower. Also, being a non-impact type, the ink jet recording apparatus makes a lesser amount of noises when in use. Further, among some other advantages, this apparatus makes it easier to recording color images using ink of multiple colors. Particularly, the line type ink jet recording apparatus using a multiple type recording means, which is provided with a plurality of discharge ports arranged in the width direction of the recording sheet, makes recording executable at a higher speed.
The ink jet type recording means (recording head) that discharges ink by the utilization of thermal energy, in particular, can be produced more easily to provide a highly densified arrangement of liquid flow paths (the arrangement of discharge ports) by forming the electrothermal transducing devices filmed on a substrate, together with electrodes, liquid flow path walls, a ceiling plate, and the like, through semiconductor manufacturing processes such as etching, deposition, sputtering. In this manner, it becomes possible to attempt making the head more compact. On the other hand, however, there have been various demands, in recent years, on the use of recording media (recording materials), such as thin paper, processed paper sheet (such as perforated sheet for filing use, scored sheet, paper sheets of freer configurations) in addition to the paper sheet, thin plastic sheet, and other regular recording media. Further, there have arisen the demands even on the use of cloths or the like.
The ink jet recording apparatus described above is to record by discharging ink from discharge ports formed on the recording head thereof. For such ink jet recording apparatus, finely arranged discharge ports are used. Therefore, if air bubbles or dust particles enter the discharge ports or if the viscosity of ink has increased due to the evaporation of ink solvent, ink becomes unsuitable for discharging or recording any longer (that is, ink discharges are made defective). The ink jet recording apparatus is, therefore, structured to perform discharge recovery processes as means for removing the causes of the discharge defectives by refreshing ink. As a method for executing such discharge recovery processes, a control method is adopted for the discharge recovery by discharging ink from all the discharge ports several times periodically or prior to a recording operation.
Also, in recent years, it is adopted to print (discharge) record processing liquid immediately before printing (recording) in ink (recording liquid) or immediately after having printed (recorded) in ink (recording liquid) in order to record high quality images in particular. A record processing liquid of the kind is colorless transparent processing liquid, and by overlaying the record processing liquid and ink (recording liquid) when printing, these two kinds of liquids are mixed on the recording medium before having been absorbed into such recording medium, thus promoting the fixing of the recorded images on the recording medium.
By means of such method for applying record processing liquid, it is possible to enhance the coloring, water-proofing, bleeding of ink with respect to a recording medium. Particularly, this method demonstrates a significant effect in preventing ink from running due to textures of a recording medium (paper) when using an ordinary paper sheet which is generally in use without any coating that accepts ink or the like. In this way, it is made possible to form images on such recording medium without running of ink. In other words, it has been a problem conventionally that ink (recording liquid) runs because of the texture of an ordinary sheet when the ink jet method is adopted for recording on such sheet which is generally in use for recording. In this respect, now that it has become possible to prevent ink from running by the adoption of such record processing liquid as described above, various kinds of processing liquids are being developed for more suitable uses depending on the properties of ink and recording media of various kinds.
Here, in accordance with the discharge recovery control method of the conventional art described above, it is arranged to make the frequency of discharges for recovery constant and equal per discharge port. As a result, the discharge frequency tends to be much more than the frequency actually needed for the discharge recovery operations required. Thus, ink may be used wastefully in some cases. Also, in accordance with the discharge recovery process of the conventional art, the recording operation (record printing) should be suspended for the discharge recovery operation after shifting the recording head to the discharge recovery position where the ink receptacle is provided for use of the discharge recovery. Consequently, there also arises a problem that such discharge recovery method inevitably brings about the slowdown of printing speed.
Particularly when the record processing liquid is used, the condition that requires the discharge recovery process or the condition that makes discharging unsuitable for recording takes place more often following the evaporation of solvent, because of its higher viscosity than that of ink. As a result, the problem referred to in the preceding paragraph becomes more conspicuous with the adoption of the conventional discharge recovery method described above.
Also, if the discharge recovery operation is performed for the record processing liquid by use of the same ink receptacle used for the ink discharge recovery operation, the record processing liquid and ink are mixed in such receptacle, resulting in the immediate solidification of discarded liquid to make it impossible to remove such solidified liquid from the receptacle. Therefore, a receptacle should be arranged only to receive record processing liquid separately from the one to be used for receiving ink. Then, this arrangement necessitates making the recording apparatus larger inevitably. Also, even if a separate receptacle is arranged to receive the record processing liquid, it is still necessary to discharge the record processing liquid and ink several times simultaneously in a short period of time in a narrow place arranged for the simultaneous operation of such discharge recovery. As a result, a large mount of mist (fine droplets) is generated, and foreign substances are solidified and fixed due to such generation of mist eventually. This is another problem encountered in this respect.